Carel MasterAria, Руководство пользователя

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26
ENG
MasterAria +030220481 - rel. 1.0 - 12.11.2007
Below is a graph showing an example of confi guration with proportional
control only (integration time = P108=0) and the trend in the OPENING
event.
100%
TA (°C)
P110
P01
P113 P116 P115
P114 P114
P109 P109
U
VC VF
S S
Fig. 4.k.a
Key:
P01 set point U outputs
P109 dead band TA room temperature
(control probe)
P110 heating valve on delta
P113 cooling valve on delta
S outside damper
P114 damper prop. band VF cooling valve
P115 cooling valve prop. band VC heating valve
P116 heating valve prop. band
Note that:
the control signal is sent to the actuators outside of the dead band
•
the valve has a proportional band for heating and another for cooling
•
the actuators are activated in sequence: fi rst the damper, then the
•
valve, which will begin opening outside of the damper proportional
band, as illustrated in the fi gure.
In this case, the valve is activated when the damper is completely open,
with a control signal corresponding to the percentage of opening at that
point (>0%). As regards CLOSING, fi rst the valve will close completely
and then the damper will start closing, at a temperature equal to the
complete closing temperature of the valve plus a ΔT equal to two times
the dead band:
ΔT = 2*P109
100%
TA (°C)
P110
2xP109
P01
P116
P114
P109
U
VC
S
Fig. 4.k.b
Key:
P01 set point U outputs
P109 dead band TA room temperature
(control probe)
P110 heating valve on delta
P113 cooling valve on delta
S outside damper
P114 damper prop. band VC heating valve
P116 heating valve prop. band
The behaviour for closing in cooling is similar but opposite.
(*) Note that as there are a maximum of two modulating 0 to 10 Vdc outputs,
the heater can be controlled with the P+I algorithm only if the damper is on/
off . The activation delta and the proportional band are parameters P111 and
P117.
Proportional and integral control - PI
If the integration time ≠ 0, the P+I algorithm is implemented. The following
graph shows the case of OPENING when the proportional band for the
damper and the hot and cold water valves have the same value, with the
activation delta set to zero.
OPENING IN HEATING:
the actuators follow a ramp trend, without steps. When the damper
•
is completely open, the valve starts opening gradually, as the error
increases due to the contribution of the integration factor;
CLOSING IN HEATING:
the valve starts closing when the room temperature exceeds point A.
•
When the valve is completely closed, the damper starts closing, until
reaching the minimum position (20%).
BEHAVIOUR IN THE DEAD BAND:
around the set point (±P109) the actuators stop at the position
•
calculated when entering the dead band.
100%
TA (°C)
P109
P01
P109
A
P114=P116
P119=20
U
VC
S
Fig. 4.k.c
Key:
P01 set point U outputs
P109 dead band TA room temperature
(control probe)
P110 heating valve on delta
P113 cooling valve on delta
S outside damper
P114 damper prop. band VC heating valve
P116 heating valve prop. band
The behaviour for opening and closing in cooling is similar but opposite.
Actuator movement control
(parameter 99)
A parameter is available that limits the movements of the valve so as to
reduce wear and adapt the P+I output to the eff ective resolution for the
position of the actuator. In fact, a minimum variation in the P+I output can
be established before the output eff ectively switches (parameter P99).
Reduction in the eff ect of changing modes and/or
operating parameters (bumpless transfer)
(parameter 107)
The “bumpless transfer” parameter, in response to changes in the P+I
algorithm control parameters during the normal operation of the unit,
dampens any swings or over-corrections of the system, especially when
the algorithm interacts with multiple devices or actuators.
Modulating valve/damper management
(parameters 97,102,103)
For modulating management of the actuators, parameters P15, P16, P17
must all be set >0.
For correct use of the 3-point actuators, the time taken for complete
opening or closing must be entered.